I think you underestimate the knowledge and skill that comes into being a support, even one like soraka. Sure you can jump slightly higher in elo then you should be able to spamming a champion with a low skill floor like soraka, doing okay, and then relying on the rest of your team to carry. However, you can do that with practically any role. While support is low on mechanics and pure skill, there is a lot more knowledge that the average support needs to have compared to other roles. You're the main warder, so you need to know what parts of the map have to be warded when, or else someone could die for it, they could get free objectives, or you can easily walk into a trap. In teamfights you need at least a little bit of knowledge of all roles, because if you don't you might not heal the jax who could have killed their adc instead of wasting the heal on your adc who would have survived, or silenced the jayce whose cooldowns are down instead of the ryze who is spamming spells, or exhausted their adc instead of the annie who hasn't ulted yet.